During chemical vapor deposition (CVD) of silicon oxide and other layers onto the surface of a substrate, the deposition gases released inside the processing chamber may cause unwanted deposition on areas such as the walls of the processing chamber. Unless removed, this unwanted deposition is a source of particles that may interfere with subsequent processing steps and adversely effect wafer yield.
To avoid such problems, the inside surface of the chamber is regularly cleaned to remove the unwanted deposition material from the chamber walls and similar areas of the processing chamber. This procedure is performed as a standard chamber dry clean operation where an etchant gas, such as nitrogen trifluoride (NF3), is used to remove (etch) the deposited material from the chamber walls and other areas. During the dry clean operation, the chamber interior is exposed to products formed by a plasma of the etchant gas which reacts with and removes the deposited material from the chamber walls. Such cleaning procedures are commonly performed between deposition steps for every wafer or every n wafers.
The clean step can, in itself, be a source of particle accumulation, however. Fluorine from the clean plasma can be absorbed and/or trapped in the chamber walls and in other areas of the chamber such as areas that include ceramic lining or other insulation material. The trapped fluorine can be released during subsequent processing steps (e.g., by reacting with constituents from the plasma in a high density plasma CVD (HDP-CVD) step) and can be absorbed in subsequently deposited silicon oxide or other layers.
To prevent such fluorine release and to provide protection against other contaminants within the chamber walls, e.g., the diffusion of sodium, aluminum, and other contaminants, a CVD chamber is often “seasoned” after the dry clean operation. Typically, seasoning includes depositing a thin silicon oxide layer over the chamber walls before a substrate is introduced into the chamber for processing. The deposited silicon oxide layer covers the chamber walls reducing the likelihood that contaminates will interfere with subsequent processing steps. After deposition of the seasoning layer is complete, the chamber is used for one to n substrate deposition steps before being cleaned in another clean operation as described above and then reseasoned.
Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. In order to achieve such decreased devices sizes and increased integration density, new and modified deposition and etch processes have been developed by the semiconductor industry. In some instances, procedures used with prior technology do not provide optimal results with new technology. Accordingly, new techniques for working with such new technology are continuously being sought including improved processes to deposit seasoning films.